蔡家湾汉江特大桥深水基础钢套箱围堰施工技术

Construction Techniques of Steel Boxed Cofferdams for Deep Water Foundations of Caijiawan Hanjiang River Bridge

蔡家湾汉江特大桥167号、168号墩的深水基础采用"先平台后围堰"方案施工。先搭设钢栈桥和钻孔平台进行钻孔桩施工,同步进行双壁钢套箱围堰的设计与加工,利用钻孔平台进行围堰的拼装,采用千斤顶起吊系统下放围堰到设计标高后,进行围堰清基、封底、抽水和承台施工。在该方案实施过程中,采取桩基钻孔与围堰拼装、围堰接高与吸泥下沉、围堰下沉与钢护筒内清渣等工序之间平行作业的方式,节省了工期;巧妙地使用千斤顶和分配梁上的2个螺栓,采用千斤顶起吊系统使围堰下放平稳、安全;根据施工水位对围堰封底厚度进行优化以节约成本。

The deep water foundations of Piers No. 167 and No. 168 of Caijiawan Hanjiang River Bridge were constructed by the scheme of ＂building the platform first and the cofferdam late＂. The steel trestle was erected and a boring platform was built first to carry out the construction of the bored piles. At the same time, a double-wall steel boxed cofferdam was designed and manufactured. The platform was used to assemble the cofferdam, the cofferdam was then low- ered down into river by the jacking-up system. Once the cofferdam was sunk to the designed elevation, the base inside the cofferdam was cleared off, sealed, the water inside was pumped out and finally the construction of the pile cap would proceed. In the implementation of the scheme, the pile foundation hole boring, the cofferdam assembling, height extension, dredging, sinking and mud clearing-off inside the steel casings were operated in a parallel way and the construction time schedule was shortened. The jacks and the two bolts on the distribution beams were ingeniously utilized. The lowering of the cofferdam into the river by the jacking-up system was stable and safe. The thickness of the basing sealing was optimized in accordance with the construction water levels and the construction cost was therefore saved.